Furnace for glowing molds for metal castings.



Patented Dec. 30, I902.

H ELMIIVIST.

FURNACE FOB GLOWING MULDS FOR METAL CASTINGS.

(Application filed Nov. 27, 1901.)

(No Model.)

TN: NORRIS nznzns so. uoro-umo, \VASWNGTON. u. c

UNITED STATES PATENT OFFICE.

HUGO ELMQVIST, OF FLORENCE, ITALY.

FURNACE FOR GLOWING IVIOLDS FOR METAL CASTINGS.

SPECIFICATION forming part of Letters Patent No. 717,086, dated December 30, 1902.

Application filed November 27, 1901. derial No. 83,910. (No model.)

To all whom it may concern.-

Be it known that I, HUGO ELMQVIST, a subject of the King of Sweden and Norway, residing at Florence, Italy, have invented certain new and useful Improvements in Furnaces for Glowing Molds for Metal Castings; and I do hereby declare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which it appertains to make and use the same,reference being had to the accompanying drawings, and to letters of reference marked thereon, which form a part of this specification.

In the casting of objects of art in metal it is necessary to thoroughly dry the mold by glowing it before the casting takes place in order to obviate the danger of the mold bursting when the molten metal is poured in. During this glowing, however, the mold loses in strength as the binding material entering into the composition of the material of which.

the mold is constituted is either vaporized or in some way loses its binding properties. For this reason it has been found advantageous to add a substance to the material of which the mold is formed which assumes the role of binding material during the glowing and retains this property. In order to impart to this substance the desired binding properties during the glowing operation, it is necessary that this operation should be effected at a considerably higher temperature than has hitherto been the case, and it is equally important that the heat should act evenly and uniformly upon the whole of the substance of the mold. To attain this, a special oven or furnace is requisite, and the provision of such a furnace forms the subject of this invention.

The invention is illustrated in the accompanying drawings, in which- Figure 1 is a vertical section through the furnace, and Fig. 2 is a horizontal section through the same.

One of the main characteristics of my improved furnace consists in the fact that the draft necessaryfor the fire does not come into contact with the substance of the mold. In

order to secure this, the furnace is provided with a hermetically-closed chamber or muffie, in which the mold is placed during the glowing operation. The hotcombustion-gases generated in the furnaces are caused to circulate as long as possible aroung the muffle containing the mold. The muflie b is arranged directly within the outer wall a of the furnace. This muffle is traversed by a central flue, which communicates with the chamber beneath the muffle, and this latterin turn communicates with thefour grates e, into which the fuel is introduced by means of the stokeholes f.

As shown in the drawings, the grates are in direct communication with the space or chamber surrounding the muffle b. In order to permit'of uniform circulation of the combustiongases around the muffie b and complete utilization of the heat of these gases, a flue i is formed in the wall CL and opens laterally into each grate. The air entering through these fines causes the flame in each grate to strike against the side opposite to the said flue, and in this manner the heat from each of the grates is uniformly distributed and circulates spirally around the muffle. The velocity of this spirally-ascending movement of the combustion-gases may be regulated by means of the ash-pit doors 7c. The wider these doors are opened the more rapidly will the hot gases pass upward. Both the outer wall a of the furnace and the muffle b are built up of annular sections of fireproof material arranged one upon the other. According to the height towhich it is desired to build the furnace a greater or smaller number of these sections are superposed. When desired, the central passage or chamber in the muifie may be dispensed with, the openings in the top and bottom of the muffle being closed. The molds to be heated are arranged in the annular chamber of the muffle, shelves being provided for their reception, if necessary. In order to indicate when the temperature has reached a point sufficient to complete the operation, a pyrometer is provided in the muffle.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is- In an oven for glowing molds for metal casting, the combination of a kiln, a mufiie centrally arranged therein, a plurality of furnaces each opening below and around said my invention I have signed my name in presmuffie, and a flue for each furnace-opening ence of two subscribing witnesses. therein on one side thereof for forcing the heat from each of the furnaces to circulate HUGO ELMQVIS-T' 5 spirally around the muflie, substantially as Witnesses:

for the purpose described. F. HADIN,

In testimony that I claim the foregoing as J. OSTLUND. 

